1. Field of the Invention
This invention relates generally to burners for combustible material and, more particularly, is directed to a burner nozzle assembly for a gas burner.
2. Description of the Prior Art
With burner assemblies, it is desirable to provide accurate adjustment of the amount of fluid utilized in the burner assembly. To this end, it is known to adjust the oil or gas flow in an oil or gas burner by means of a nozzle having a plurality of orifice plugs which are axially movable with respect to the opening of the nozzle. Examples of such arrangements are shown and disclosed in U.S. Pat. Nos. 1,696,196; 1,781,236 and 3,771,944; and Japanese Patent Publication Nos. 57-105611 and 57-161411. Outside of the burner art, see U.S. Pat. Nos. 775,156 and 1,561,809.
Further, U.S. Pat. No. 3,684,192 discloses a single nozzle, outside of the burner art, which provides constant pressure, variable flow, regardless of the pressure from the source.
U.S. Pat. No. 4,285,664 to the same inventor herein discloses a burner for a plurality of fluid streams and is generally of the type to which the present invention is directed. With the burner of this latter apparatus, however, there is no adjustment of the gas pressure or velocity at the outlet side of the burner nozzle. This patent also discloses a bluff body effect which is produced by the flat downstream end of a velocity ring by which a toroidal eddy is produced.
With the above burner patents, for example, that shown in U.S. Pat. No. 1,781,236, where a plurality of curcumferentially arranged orifices are provided along with a plurality of circumferentially arranged orifice plugs which are axially movable toward and away from the respective orifices, a problem occurs with mounting the orifice plugs so as not to interfere with the axial and linear flow of the gas to the orifices, while at the same time, providing for a constant velocity flow of gas from the orifices.
Attention is also drawn to U.S. Pat. Nos. 1,024,596; 1,584,546; 2,978,188; 3,102,446; 3,243,127; British Pat. No. 1,441,750; French Pat. No. 786,155; PCT Publication No. 8101668; and USSR Pat. No. 47,905.
Related to the problem of providing accurate adjustment of the amount of fluid utilized in a burner assembly, in sludge lime kiln stacks, emission requirements call for the total residual sulfides (TRS) to be less than 20 parts per million (PPM). This emission requirement is difficult to achieve with conventional burner assemblies which do not provide accurate adjustment of the amount of fluid utilized in the burner assembly. Such emission requirements can not be met with a burner assembly of the aforementioned type in which the orifices are arranged circumferentially.
Further, with the aforementioned U.S. Patents, the use of conical or frusto-conical shaped orifice plugs results in a relatively slow non-linear response curve for the flow of natural gas. It therefore further becomes difficult to achieve the aforementioned emission requirements.
A further problem occurs with respect to radial duct burners. More particularly, with rotary kilns, such as that shown in U.S. Pat. No. 1,781,236, to control the orifice openings, it is only necessary to axially move the shaft which is connected to the orifice plugs. In a radial duct burner, however, the orifice openings are arranged circumferentially in the radial direction. Thus, mere axial movement of a shaft is not possible for controlling movement of the orifice plugs.